CAPE TOWN (Reuters) - The corruption trial of former South African president Jacob Zuma for a $2 billion government arms deal has been postponed to Oct. 26, the presiding judge said on Wednesday.

       Judge Piet Koen said he will try to deliver judgement then on Zuma's plea to have the lead prosecutor, Billy Downer, removed from a case he has been involved in for almost two decades because of perceptions that Downer was biased and not impartial.

       "I will try and hopefully have the judgment ready by then," Koen said before adjourning the Pietermaritzburg High Court.

       The trial over a 1990s deal was meant to start in May, but has been postponed a number of times due to legal arguments and Zuma's unavailability.

       Zuma, 79, and suffering from an undisclosed illness, was absent from proceedings at the Pietermaritzburg High Court on Tuesday and Wednesday. Zuma had surgery in August, but it is not clear what the surgery was for.

       He has pleaded not guilty to charges of corruption, money laundering and racketeering related to the acquisition of military equipment.

       In particular he is accused of receiving kickbacks over a 1999 deal with French arms group Thales in exchange for protecting the company from investigation. He has pleaded not guilty to all charges, and Thales has denied wrongdoing.

       On July 7, Zuma was jailed for failing to cooperate with a separate corruption probe, precipitating some of the worst riots and looting the country has seen since the end of white minority rule in 1994. More than 300 people were killed and thousands of businesses looted.

       On Friday the Constitutional Court dismissed a bid by Zuma to overturn his 15-month jail sentence for contempt of court after he ignored instructions to participate in a corruption inquiry.

       (Reporting by Wendell Roelf; Editing by Hugh Lawson)